In high-speed printing apparatus, such as high-speed magnetic ink character recognition (MICR) encoders in which the print speed may exceed 300 documents per minute, advancing and controlling of the ink ribbon used in such apparatus is a major problem, which becomes more difficult as speed increases.
In all high-speed MICR printers, the consumption of ribbon is very high. Therefore, the quantity of ribbon on the ribbon supply roll is very high. Since the mass of such ribbon is large, the moment of inertia is also very large. Initially a large force is required to move the ribbon, due to its relatively large mass on the supply roll. Ribbon breakage is a common problem, due to the necessity for application of a large pulling force on a large mass. Once the ribbon starts moving, the large inertial force of the ribbon supply keeps it moving. A high degree of precision and a well-controlled braking mechanism are required to keep the ribbon from becoming slack along its path from the supply roll to the take-up roll.